I've been working on fixing GDC/MinGW's runtime support. I ran across the following and was hoping to get a clarification on what DMD does differently than GDC.
void testexp()
{
printf("exp(3.0) = %Lg, %Lg\n", exp(3.0), E * E * E);
assert(equals(exp(3.0), E * E * E, 16));
}
Of interest is exp(3.0). GDC matches exp(3.0) to double exp(double). This causes problems with printf due to %Lg wanting a real but only receiving a double.
Looking at the D specification for overloading functions.
1. no match
2. match with implicit conversions
3. match with conversion to const
4. exact match
The specification doesn't indicate what levels are better. I would guess 4 is the best since an exact match should take precedence.
However, that results in GDC matching exp(3.0) to double exp(double).
How does DMD match exp(3.0)?
Could it possibly be a typo? For 32-bit this test passes because the printf doesn't segfault, it's only noticeable with 64-bit since it segfaults.

On 1/13/2012 10:51 PM, Daniel Green wrote:
> Could it possibly be a typo? For 32-bit this test passes because the printf
> doesn't segfault, it's only noticeable with 64-bit since it segfaults.
3.0 should match double, when there is both double and real.

I think the only difference may be that gdc possibly folds the call to
exp().
Check the difference between what code gdc generates compared to how gcc processed it: -fdump-tree-original -fdump-tree-optimized
----
Iain Buclaw
*(p < e ? p++ : p) = (c & 0x0f) + '0';
On 14 Jan 2012 06:56, "Daniel Green" <venix1@gmail.com> wrote:
>> I've been working on fixing GDC/MinGW's runtime support. I ran across
the following and was hoping to get a clarification on what DMD does differently than GDC.
>> void testexp()
> {
> printf("exp(3.0) = %Lg, %Lg\n", exp(3.0), E * E * E);
> assert(equals(exp(3.0), E * E * E, 16));
> }
>> Of interest is exp(3.0). GDC matches exp(3.0) to double exp(double).
This causes problems with printf due to %Lg wanting a real but only receiving a double.
>> Looking at the D specification for overloading functions.
> 1. no match
> 2. match with implicit conversions
> 3. match with conversion to const
> 4. exact match
>>> The specification doesn't indicate what levels are better. I would guess
4 is the best since an exact match should take precedence.
> However, that results in GDC matching exp(3.0) to double exp(double).
>> How does DMD match exp(3.0)?
>> Could it possibly be a typo? For 32-bit this test passes because the
printf doesn't segfault, it's only noticeable with 64-bit since it segfaults.

On 1/14/2012 3:29 AM, Walter Bright wrote:
> On 1/13/2012 10:51 PM, Daniel Green wrote:
>> Could it possibly be a typo? For 32-bit this test passes because the
>> printf
>> doesn't segfault, it's only noticeable with 64-bit since it segfaults.
>> 3.0 should match double, when there is both double and real.
On 1/14/2012 3:29 AM, Walter Bright wrote:
> On 1/13/2012 10:51 PM, Daniel Green wrote:
>> Could it possibly be a typo? For 32-bit this test passes because the
>> printf
>> doesn't segfault, it's only noticeable with 64-bit since it segfaults.
>
> 3.0 should match double, when there is both double and real.
When I run the following through DMD r is type real. For GDC r is type double.
The matched function would be
double exp(double x) @safe pure nothrow { return exp(cast(real)x); }.
Is it expected that DMD promotes a double to real?
// GDC: r is type double
// DMD: r is type real
import std.stdio;
import std.math;
void main()
{
auto r = exp(3.0);
writefln("%s", typeof(r).stringof);
}

On 1/14/2012 10:34 AM, Iain Buclaw wrote:
> Strange, I get 'double' for both DMD and GDC... is this maybe a Windows thing?
Just ran it with linux and got 'double' as well. So it appears to be a Windows thing.